/*
 * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package com.sun.org.apache.bcel.internal.generic;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache BCEL" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache BCEL", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

import com.sun.org.apache.bcel.internal.Constants;
import com.sun.org.apache.bcel.internal.classfile.Constant;
import com.sun.org.apache.bcel.internal.util.ByteSequence;
import java.io.*;
import java.util.Iterator;
import java.util.HashMap;
import java.util.ArrayList;

/**
 * This class is a container for a list of <a
 * href="Instruction.html">Instruction</a> objects. Instructions can
 * be appended, inserted, moved, deleted, etc.. Instructions are being
 * wrapped into <a
 * href="InstructionHandle.html">InstructionHandles</a> objects that
 * are returned upon append/insert operations. They give the user
 * (read only) access to the list structure, such that it can be traversed and
 * manipulated in a controlled way.
 *
 * A list is finally dumped to a byte code array with <a
 * href="#getByteCode()">getByteCode</a>.
 *
 * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
 * @see Instruction
 * @see InstructionHandle
 * @see BranchHandle
 */
public class InstructionList implements Serializable {

  private InstructionHandle start = null, end = null;
  private int length = 0; // number of elements in list
  private int[] byte_positions; // byte code offsets corresponding to instructions

  /**
   * Create (empty) instruction list.
   */
  public InstructionList() {
  }

  /**
   * Create instruction list containing one instruction.
   *
   * @param i initial instruction
   */
  public InstructionList(Instruction i) {
    append(i);
  }

  /**
   * Create instruction list containing one instruction.
   *
   * @param i initial instruction
   */
  public InstructionList(BranchInstruction i) {
    append(i);
  }

  /**
   * Initialize list with (nonnull) compound instruction. Consumes argument
   * list, i.e., it becomes empty.
   *
   * @param c compound instruction (list)
   */
  public InstructionList(CompoundInstruction c) {
    append(c.getInstructionList());
  }

  /**
   * Test for empty list.
   */
  public boolean isEmpty() {
    return start == null;
  } // && end == null

  /**
   * Find the target instruction (handle) that corresponds to the given target
   * position (byte code offset).
   *
   * @param ihs array of instruction handles, i.e. il.getInstructionHandles()
   * @param pos array of positions corresponding to ihs, i.e. il.getInstructionPositions()
   * @param count length of arrays
   * @param target target position to search for
   * @return target position's instruction handle if available
   */
  public static InstructionHandle findHandle(InstructionHandle[] ihs,
      int[] pos, int count,
      int target) {
    int l = 0, r = count - 1;

    /* Do a binary search since the pos array is orderd.
     */
    do {
      int i = (l + r) / 2;
      int j = pos[i];

      if (j == target) // target found
      {
        return ihs[i];
      } else if (target < j) // else constrain search area
      {
        r = i - 1;
      } else // target > j
      {
        l = i + 1;
      }
    } while (l <= r);

    return null;
  }

  /**
   * Get instruction handle for instruction at byte code position pos.
   * This only works properly, if the list is freshly initialized from a byte array or
   * setPositions() has been called before this method.
   *
   * @param pos byte code position to search for
   * @return target position's instruction handle if available
   */
  public InstructionHandle findHandle(int pos) {
    InstructionHandle[] ihs = getInstructionHandles();
    return findHandle(ihs, byte_positions, length, pos);
  }

  /**
   * Initialize instruction list from byte array.
   *
   * @param code byte array containing the instructions
   */
  public InstructionList(byte[] code) {
    ByteSequence bytes = new ByteSequence(code);
    InstructionHandle[] ihs = new InstructionHandle[code.length];
    int[] pos = new int[code.length]; // Can't be more than that
    int count = 0; // Contains actual length

    /* Pass 1: Create an object for each byte code and append them
     * to the list.
     */
    try {
      while (bytes.available() > 0) {
        // Remember byte offset and associate it with the instruction
        int off = bytes.getIndex();
        pos[count] = off;

        /* Read one instruction from the byte stream, the byte position is set
         * accordingly.
         */
        Instruction i = Instruction.readInstruction(bytes);
        InstructionHandle ih;
        if (i instanceof BranchInstruction) // Use proper append() method
        {
          ih = append((BranchInstruction) i);
        } else {
          ih = append(i);
        }

        ih.setPosition(off);
        ihs[count] = ih;

        count++;
      }
    } catch (IOException e) {
      throw new ClassGenException(e.toString());
    }

    byte_positions = new int[count]; // Trim to proper size
    System.arraycopy(pos, 0, byte_positions, 0, count);

    /* Pass 2: Look for BranchInstruction and update their targets, i.e.,
     * convert offsets to instruction handles.
     */
    for (int i = 0; i < count; i++) {
      if (ihs[i] instanceof BranchHandle) {
        BranchInstruction bi = (BranchInstruction) ihs[i].instruction;
        int target = bi.position + bi.getIndex(); /* Byte code position:
                                                   * relative -> absolute. */
        // Search for target position
        InstructionHandle ih = findHandle(ihs, pos, count, target);

        if (ih == null) // Search failed
        {
          throw new ClassGenException("Couldn't find target for branch: " + bi);
        }

        bi.setTarget(ih); // Update target

        // If it is a Select instruction, update all branch targets
        if (bi instanceof Select) { // Either LOOKUPSWITCH or TABLESWITCH
          Select s = (Select) bi;
          int[] indices = s.getIndices();

          for (int j = 0; j < indices.length; j++) {
            target = bi.position + indices[j];
            ih = findHandle(ihs, pos, count, target);

            if (ih == null) // Search failed
            {
              throw new ClassGenException("Couldn't find target for switch: " + bi);
            }

            s.setTarget(j, ih); // Update target
          }
        }
      }
    }
  }

  /**
   * Append another list after instruction (handle) ih contained in this list.
   * Consumes argument list, i.e., it becomes empty.
   *
   * @param ih where to append the instruction list
   * @param il Instruction list to append to this one
   * @return instruction handle pointing to the <B>first</B> appended instruction
   */
  public InstructionHandle append(InstructionHandle ih, InstructionList il) {
    if (il == null) {
      throw new ClassGenException("Appending null InstructionList");
    }

    if (il.isEmpty()) // Nothing to do
    {
      return ih;
    }

    InstructionHandle next = ih.next, ret = il.start;

    ih.next = il.start;
    il.start.prev = ih;

    il.end.next = next;

    if (next != null) // i == end ?
    {
      next.prev = il.end;
    } else {
      end = il.end; // Update end ...
    }

    length += il.length; // Update length

    il.clear();

    return ret;
  }

  /**
   * Append another list after instruction i contained in this list.
   * Consumes argument list, i.e., it becomes empty.
   *
   * @param i where to append the instruction list
   * @param il Instruction list to append to this one
   * @return instruction handle pointing to the <B>first</B> appended instruction
   */
  public InstructionHandle append(Instruction i, InstructionList il) {
    InstructionHandle ih;

    if ((ih = findInstruction2(i)) == null) // Also applies for empty list
    {
      throw new ClassGenException("Instruction " + i +
          " is not contained in this list.");
    }

    return append(ih, il);
  }

  /**
   * Append another list to this one.
   * Consumes argument list, i.e., it becomes empty.
   *
   * @param il list to append to end of this list
   * @return instruction handle of the <B>first</B> appended instruction
   */
  public InstructionHandle append(InstructionList il) {
    if (il == null) {
      throw new ClassGenException("Appending null InstructionList");
    }

    if (il.isEmpty()) // Nothing to do
    {
      return null;
    }

    if (isEmpty()) {
      start = il.start;
      end = il.end;
      length = il.length;

      il.clear();

      return start;
    } else {
      return append(end, il);  // was end.instruction
    }
  }

  /**
   * Append an instruction to the end of this list.
   *
   * @param ih instruction to append
   */
  private void append(InstructionHandle ih) {
    if (isEmpty()) {
      start = end = ih;
      ih.next = ih.prev = null;
    } else {
      end.next = ih;
      ih.prev = end;
      ih.next = null;
      end = ih;
    }

    length++; // Update length
  }

  /**
   * Append an instruction to the end of this list.
   *
   * @param i instruction to append
   * @return instruction handle of the appended instruction
   */
  public InstructionHandle append(Instruction i) {
    InstructionHandle ih = InstructionHandle.getInstructionHandle(i);
    append(ih);

    return ih;
  }

  /**
   * Append a branch instruction to the end of this list.
   *
   * @param i branch instruction to append
   * @return branch instruction handle of the appended instruction
   */
  public BranchHandle append(BranchInstruction i) {
    BranchHandle ih = BranchHandle.getBranchHandle(i);
    append(ih);

    return ih;
  }

  /**
   * Append a single instruction j after another instruction i, which
   * must be in this list of course!
   *
   * @param i Instruction in list
   * @param j Instruction to append after i in list
   * @return instruction handle of the first appended instruction
   */
  public InstructionHandle append(Instruction i, Instruction j) {
    return append(i, new InstructionList(j));
  }

  /**
   * Append a compound instruction, after instruction i.
   *
   * @param i Instruction in list
   * @param c The composite instruction (containing an InstructionList)
   * @return instruction handle of the first appended instruction
   */
  public InstructionHandle append(Instruction i, CompoundInstruction c) {
    return append(i, c.getInstructionList());
  }

  /**
   * Append a compound instruction.
   *
   * @param c The composite instruction (containing an InstructionList)
   * @return instruction handle of the first appended instruction
   */
  public InstructionHandle append(CompoundInstruction c) {
    return append(c.getInstructionList());
  }

  /**
   * Append a compound instruction.
   *
   * @param ih where to append the instruction list
   * @param c The composite instruction (containing an InstructionList)
   * @return instruction handle of the first appended instruction
   */
  public InstructionHandle append(InstructionHandle ih, CompoundInstruction c) {
    return append(ih, c.getInstructionList());
  }

  /**
   * Append an instruction after instruction (handle) ih contained in this list.
   *
   * @param ih where to append the instruction list
   * @param i Instruction to append
   * @return instruction handle pointing to the <B>first</B> appended instruction
   */
  public InstructionHandle append(InstructionHandle ih, Instruction i) {
    return append(ih, new InstructionList(i));
  }

  /**
   * Append an instruction after instruction (handle) ih contained in this list.
   *
   * @param ih where to append the instruction list
   * @param i Instruction to append
   * @return instruction handle pointing to the <B>first</B> appended instruction
   */
  public BranchHandle append(InstructionHandle ih, BranchInstruction i) {
    BranchHandle bh = BranchHandle.getBranchHandle(i);
    InstructionList il = new InstructionList();
    il.append(bh);

    append(ih, il);

    return bh;
  }

  /**
   * Insert another list before Instruction handle ih contained in this list.
   * Consumes argument list, i.e., it becomes empty.
   *
   * @param i where to append the instruction list
   * @param il Instruction list to insert
   * @return instruction handle of the first inserted instruction
   */
  public InstructionHandle insert(InstructionHandle ih, InstructionList il) {
    if (il == null) {
      throw new ClassGenException("Inserting null InstructionList");
    }

    if (il.isEmpty()) // Nothing to do
    {
      return ih;
    }

    InstructionHandle prev = ih.prev, ret = il.start;

    ih.prev = il.end;
    il.end.next = ih;

    il.start.prev = prev;

    if (prev != null) // ih == start ?
    {
      prev.next = il.start;
    } else {
      start = il.start; // Update start ...
    }

    length += il.length; // Update length

    il.clear();

    return ret;
  }

  /**
   * Insert another list.
   *
   * @param il list to insert before start of this list
   * @return instruction handle of the first inserted instruction
   */
  public InstructionHandle insert(InstructionList il) {
    if (isEmpty()) {
      append(il); // Code is identical for this case
      return start;
    } else {
      return insert(start, il);
    }
  }

  /**
   * Insert an instruction at start of this list.
   *
   * @param ih instruction to insert
   */
  private void insert(InstructionHandle ih) {
    if (isEmpty()) {
      start = end = ih;
      ih.next = ih.prev = null;
    } else {
      start.prev = ih;
      ih.next = start;
      ih.prev = null;
      start = ih;
    }

    length++;
  }

  /**
   * Insert another list before Instruction i contained in this list.
   * Consumes argument list, i.e., it becomes empty.
   *
   * @param i where to append the instruction list
   * @param il Instruction list to insert
   * @return instruction handle pointing to the first inserted instruction, i.e., il.getStart()
   */
  public InstructionHandle insert(Instruction i, InstructionList il) {
    InstructionHandle ih;

    if ((ih = findInstruction1(i)) == null) {
      throw new ClassGenException("Instruction " + i +
          " is not contained in this list.");
    }

    return insert(ih, il);
  }

  /**
   * Insert an instruction at start of this list.
   *
   * @param i instruction to insert
   * @return instruction handle of the inserted instruction
   */
  public InstructionHandle insert(Instruction i) {
    InstructionHandle ih = InstructionHandle.getInstructionHandle(i);
    insert(ih);

    return ih;
  }

  /**
   * Insert a branch instruction at start of this list.
   *
   * @param i branch instruction to insert
   * @return branch instruction handle of the appended instruction
   */
  public BranchHandle insert(BranchInstruction i) {
    BranchHandle ih = BranchHandle.getBranchHandle(i);
    insert(ih);
    return ih;
  }

  /**
   * Insert a single instruction j before another instruction i, which
   * must be in this list of course!
   *
   * @param i Instruction in list
   * @param j Instruction to insert before i in list
   * @return instruction handle of the first inserted instruction
   */
  public InstructionHandle insert(Instruction i, Instruction j) {
    return insert(i, new InstructionList(j));
  }

  /**
   * Insert a compound instruction before instruction i.
   *
   * @param i Instruction in list
   * @param c The composite instruction (containing an InstructionList)
   * @return instruction handle of the first inserted instruction
   */
  public InstructionHandle insert(Instruction i, CompoundInstruction c) {
    return insert(i, c.getInstructionList());
  }

  /**
   * Insert a compound instruction.
   *
   * @param c The composite instruction (containing an InstructionList)
   * @return instruction handle of the first inserted instruction
   */
  public InstructionHandle insert(CompoundInstruction c) {
    return insert(c.getInstructionList());
  }

  /**
   * Insert an instruction before instruction (handle) ih contained in this list.
   *
   * @param ih where to insert to the instruction list
   * @param i Instruction to insert
   * @return instruction handle of the first inserted instruction
   */
  public InstructionHandle insert(InstructionHandle ih, Instruction i) {
    return insert(ih, new InstructionList(i));
  }

  /**
   * Insert a compound instruction.
   *
   * @param ih where to insert the instruction list
   * @param c The composite instruction (containing an InstructionList)
   * @return instruction handle of the first inserted instruction
   */
  public InstructionHandle insert(InstructionHandle ih, CompoundInstruction c) {
    return insert(ih, c.getInstructionList());
  }

  /**
   * Insert an instruction before instruction (handle) ih contained in this list.
   *
   * @param ih where to insert to the instruction list
   * @param i Instruction to insert
   * @return instruction handle of the first inserted instruction
   */
  public BranchHandle insert(InstructionHandle ih, BranchInstruction i) {
    BranchHandle bh = BranchHandle.getBranchHandle(i);
    InstructionList il = new InstructionList();
    il.append(bh);

    insert(ih, il);

    return bh;
  }

  /**
   * Take all instructions (handles) from "start" to "end" and append them after the
   * new location "target". Of course, "end" must be after "start" and target must
   * not be located withing this range. If you want to move something to the start of
   * the list use null as value for target.<br>
   * Any instruction targeters pointing to handles within the block, keep their targets.
   *
   * @param start of moved block
   * @param end of moved block
   * @param target of moved block
   */
  public void move(InstructionHandle start, InstructionHandle end, InstructionHandle target) {
    // Step 1: Check constraints

    if ((start == null) || (end == null)) {
      throw new ClassGenException("Invalid null handle: From " + start + " to " + end);
    }

    if ((target == start) || (target == end)) {
      throw new ClassGenException("Invalid range: From " + start + " to " + end +
          " contains target " + target);
    }

    for (InstructionHandle ih = start; ih != end.next; ih = ih.next) {
      if (ih == null) // At end of list, end not found yet
      {
        throw new ClassGenException("Invalid range: From " + start + " to " + end);
      } else if (ih == target) // target may be null
      {
        throw new ClassGenException("Invalid range: From " + start + " to " + end +
            " contains target " + target);
      }
    }

    // Step 2: Temporarily remove the given instructions from the list

    InstructionHandle prev = start.prev, next = end.next;

    if (prev != null) {
      prev.next = next;
    } else // start == this.start!
    {
      this.start = next;
    }

    if (next != null) {
      next.prev = prev;
    } else // end == this.end!
    {
      this.end = prev;
    }

    start.prev = end.next = null;

    // Step 3: append after target

    if (target == null) { // append to start of list
      end.next = this.start;
      this.start = start;
    } else {
      next = target.next;

      target.next = start;
      start.prev = target;
      end.next = next;

      if (next != null) {
        next.prev = end;
      }
    }
  }

  /**
   * Move a single instruction (handle) to a new location.
   *
   * @param ih moved instruction
   * @param target new location of moved instruction
   */
  public void move(InstructionHandle ih, InstructionHandle target) {
    move(ih, ih, target);
  }

  /**
   * Remove from instruction `prev' to instruction `next' both contained
   * in this list. Throws TargetLostException when one of the removed instruction handles
   * is still being targeted.
   *
   * @param prev where to start deleting (predecessor, exclusive)
   * @param next where to end deleting (successor, exclusive)
   */
  private void remove(InstructionHandle prev, InstructionHandle next)
      throws TargetLostException {
    InstructionHandle first, last; // First and last deleted instruction

    if ((prev == null) && (next == null)) { // singleton list
      first = last = start;
      start = end = null;
    } else {
      if (prev == null) { // At start of list
        first = start;
        start = next;
      } else {
        first = prev.next;
        prev.next = next;
      }

      if (next == null) { // At end of list
        last = end;
        end = prev;
      } else {
        last = next.prev;
        next.prev = prev;
      }
    }

    first.prev = null; // Completely separated from rest of list
    last.next = null;

    ArrayList target_vec = new ArrayList();

    for (InstructionHandle ih = first; ih != null; ih = ih.next) {
      ih.getInstruction().dispose(); // e.g. BranchInstructions release their targets
    }

    StringBuffer buf = new StringBuffer("{ ");
    for (InstructionHandle ih = first; ih != null; ih = next) {
      next = ih.next;
      length--;

      if (ih.hasTargeters()) { // Still got targeters?
        target_vec.add(ih);
        buf.append(ih.toString(true) + " ");
        ih.next = ih.prev = null;
      } else {
        ih.dispose();
      }
    }

    buf.append("}");

    if (!target_vec.isEmpty()) {
      InstructionHandle[] targeted = new InstructionHandle[target_vec.size()];
      target_vec.toArray(targeted);
      throw new TargetLostException(targeted, buf.toString());
    }
  }

  /**
   * Remove instruction from this list. The corresponding Instruction
   * handles must not be reused!
   *
   * @param ih instruction (handle) to remove
   */
  public void delete(InstructionHandle ih) throws TargetLostException {
    remove(ih.prev, ih.next);
  }

  /**
   * Remove instruction from this list. The corresponding Instruction
   * handles must not be reused!
   *
   * @param i instruction to remove
   */
  public void delete(Instruction i) throws TargetLostException {
    InstructionHandle ih;

    if ((ih = findInstruction1(i)) == null) {
      throw new ClassGenException("Instruction " + i +
          " is not contained in this list.");
    }
    delete(ih);
  }

  /**
   * Remove instructions from instruction `from' to instruction `to' contained
   * in this list. The user must ensure that `from' is an instruction before
   * `to', or risk havoc. The corresponding Instruction handles must not be reused!
   *
   * @param from where to start deleting (inclusive)
   * @param to where to end deleting (inclusive)
   */
  public void delete(InstructionHandle from, InstructionHandle to)
      throws TargetLostException {
    remove(from.prev, to.next);
  }

  /**
   * Remove instructions from instruction `from' to instruction `to' contained
   * in this list. The user must ensure that `from' is an instruction before
   * `to', or risk havoc. The corresponding Instruction handles must not be reused!
   *
   * @param from where to start deleting (inclusive)
   * @param to where to end deleting (inclusive)
   */
  public void delete(Instruction from, Instruction to) throws TargetLostException {
    InstructionHandle from_ih, to_ih;

    if ((from_ih = findInstruction1(from)) == null) {
      throw new ClassGenException("Instruction " + from +
          " is not contained in this list.");
    }

    if ((to_ih = findInstruction2(to)) == null) {
      throw new ClassGenException("Instruction " + to +
          " is not contained in this list.");
    }
    delete(from_ih, to_ih);
  }

  /**
   * Search for given Instruction reference, start at beginning of list.
   *
   * @param i instruction to search for
   * @return instruction found on success, null otherwise
   */
  private InstructionHandle findInstruction1(Instruction i) {
    for (InstructionHandle ih = start; ih != null; ih = ih.next) {
      if (ih.instruction == i) {
        return ih;
      }
    }

    return null;
  }

  /**
   * Search for given Instruction reference, start at end of list
   *
   * @param i instruction to search for
   * @return instruction found on success, null otherwise
   */
  private InstructionHandle findInstruction2(Instruction i) {
    for (InstructionHandle ih = end; ih != null; ih = ih.prev) {
      if (ih.instruction == i) {
        return ih;
      }
    }

    return null;
  }

  public boolean contains(InstructionHandle i) {
    if (i == null) {
      return false;
    }

    for (InstructionHandle ih = start; ih != null; ih = ih.next) {
      if (ih == i) {
        return true;
      }
    }

    return false;
  }

  public boolean contains(Instruction i) {
    return findInstruction1(i) != null;
  }

  public void setPositions() {
    setPositions(false);
  }

  /**
   * Give all instructions their position number (offset in byte stream), i.e.,
   * make the list ready to be dumped.
   *
   * @param check Perform sanity checks, e.g. if all targeted instructions really belong to this
   * list
   */
  public void setPositions(boolean check) {
    int max_additional_bytes = 0, additional_bytes = 0;
    int index = 0, count = 0;
    int[] pos = new int[length];

    /* Pass 0: Sanity checks
     */
    if (check) {
      for (InstructionHandle ih = start; ih != null; ih = ih.next) {
        Instruction i = ih.instruction;

        if (i instanceof BranchInstruction) { // target instruction within list?
          Instruction inst = ((BranchInstruction) i).getTarget().instruction;
          if (!contains(inst)) {
            throw new ClassGenException("Branch target of " +
                Constants.OPCODE_NAMES[i.opcode] + ":" +
                inst + " not in instruction list");
          }

          if (i instanceof Select) {
            InstructionHandle[] targets = ((Select) i).getTargets();

            for (int j = 0; j < targets.length; j++) {
              inst = targets[j].instruction;
              if (!contains(inst)) {
                throw new ClassGenException("Branch target of " +
                    Constants.OPCODE_NAMES[i.opcode] + ":" +
                    inst + " not in instruction list");
              }
            }
          }

          if (!(ih instanceof BranchHandle)) {
            throw new ClassGenException("Branch instruction " +
                Constants.OPCODE_NAMES[i.opcode] + ":" +
                inst + " not contained in BranchHandle.");
          }

        }
      }
    }

    /* Pass 1: Set position numbers and sum up the maximum number of bytes an
     * instruction may be shifted.
     */
    for (InstructionHandle ih = start; ih != null; ih = ih.next) {
      Instruction i = ih.instruction;

      ih.setPosition(index);
      pos[count++] = index;

      /* Get an estimate about how many additional bytes may be added, because
       * BranchInstructions may have variable length depending on the target
       * offset (short vs. int) or alignment issues (TABLESWITCH and
       * LOOKUPSWITCH).
       */
      switch (i.getOpcode()) {
        case Constants.JSR:
        case Constants.GOTO:
          max_additional_bytes += 2;
          break;

        case Constants.TABLESWITCH:
        case Constants.LOOKUPSWITCH:
          max_additional_bytes += 3;
          break;
      }

      index += i.getLength();
    }

    /* Pass 2: Expand the variable-length (Branch)Instructions depending on
     * the target offset (short or int) and ensure that branch targets are
     * within this list.
     */
    for (InstructionHandle ih = start; ih != null; ih = ih.next) {
      additional_bytes += ih.updatePosition(additional_bytes, max_additional_bytes);
    }

    /* Pass 3: Update position numbers (which may have changed due to the
     * preceding expansions), like pass 1.
     */
    index = count = 0;
    for (InstructionHandle ih = start; ih != null; ih = ih.next) {
      Instruction i = ih.instruction;

      ih.setPosition(index);
      pos[count++] = index;
      index += i.getLength();
    }

    byte_positions = new int[count]; // Trim to proper size
    System.arraycopy(pos, 0, byte_positions, 0, count);
  }

  /**
   * When everything is finished, use this method to convert the instruction
   * list into an array of bytes.
   *
   * @return the byte code ready to be dumped
   */
  public byte[] getByteCode() {
    // Update position indices of instructions
    setPositions();

    ByteArrayOutputStream b = new ByteArrayOutputStream();
    DataOutputStream out = new DataOutputStream(b);

    try {
      for (InstructionHandle ih = start; ih != null; ih = ih.next) {
        Instruction i = ih.instruction;
        i.dump(out); // Traverse list
      }
    } catch (IOException e) {
      System.err.println(e);
      return null;
    }

    return b.toByteArray();
  }

  /**
   * @return an array of instructions without target information for branch instructions.
   */
  public Instruction[] getInstructions() {
    ByteSequence bytes = new ByteSequence(getByteCode());
    ArrayList instructions = new ArrayList();

    try {
      while (bytes.available() > 0) {
        instructions.add(Instruction.readInstruction(bytes));
      }
    } catch (IOException e) {
      throw new ClassGenException(e.toString());
    }

    Instruction[] result = new Instruction[instructions.size()];
    instructions.toArray(result);
    return result;
  }

  public String toString() {
    return toString(true);
  }

  /**
   * @param verbose toggle output format
   * @return String containing all instructions in this list.
   */
  public String toString(boolean verbose) {
    StringBuffer buf = new StringBuffer();

    for (InstructionHandle ih = start; ih != null; ih = ih.next) {
      buf.append(ih.toString(verbose) + "\n");
    }

    return buf.toString();
  }

  /**
   * @return Enumeration that lists all instructions (handles)
   */
  public Iterator iterator() {
    return new Iterator() {
      private InstructionHandle ih = start;

      public Object next() {
        InstructionHandle i = ih;
        ih = ih.next;
        return i;
      }

      public void remove() {
        throw new UnsupportedOperationException();
      }

      public boolean hasNext() {
        return ih != null;
      }
    };
  }

  /**
   * @return array containing all instructions (handles)
   */
  public InstructionHandle[] getInstructionHandles() {
    InstructionHandle[] ihs = new InstructionHandle[length];
    InstructionHandle ih = start;

    for (int i = 0; i < length; i++) {
      ihs[i] = ih;
      ih = ih.next;
    }

    return ihs;
  }

  /**
   * Get positions (offsets) of all instructions in the list. This relies on that
   * the list has been freshly created from an byte code array, or that setPositions()
   * has been called. Otherwise this may be inaccurate.
   *
   * @return array containing all instruction's offset in byte code
   */
  public int[] getInstructionPositions() {
    return byte_positions;
  }

  /**
   * @return complete, i.e., deep copy of this list
   */
  public InstructionList copy() {
    HashMap map = new HashMap();
    InstructionList il = new InstructionList();

    /* Pass 1: Make copies of all instructions, append them to the new list
     * and associate old instruction references with the new ones, i.e.,
     * a 1:1 mapping.
     */
    for (InstructionHandle ih = start; ih != null; ih = ih.next) {
      Instruction i = ih.instruction;
      Instruction c = i.copy(); // Use clone for shallow copy

      if (c instanceof BranchInstruction) {
        map.put(ih, il.append((BranchInstruction) c));
      } else {
        map.put(ih, il.append(c));
      }
    }

    /* Pass 2: Update branch targets.
     */
    InstructionHandle ih = start;
    InstructionHandle ch = il.start;

    while (ih != null) {
      Instruction i = ih.instruction;
      Instruction c = ch.instruction;

      if (i instanceof BranchInstruction) {
        BranchInstruction bi = (BranchInstruction) i;
        BranchInstruction bc = (BranchInstruction) c;
        InstructionHandle itarget = bi.getTarget(); // old target

        // New target is in hash map
        bc.setTarget((InstructionHandle) map.get(itarget));

        if (bi instanceof Select) { // Either LOOKUPSWITCH or TABLESWITCH
          InstructionHandle[] itargets = ((Select) bi).getTargets();
          InstructionHandle[] ctargets = ((Select) bc).getTargets();

          for (int j = 0; j < itargets.length; j++) { // Update all targets
            ctargets[j] = (InstructionHandle) map.get(itargets[j]);
          }
        }
      }

      ih = ih.next;
      ch = ch.next;
    }

    return il;
  }

  /**
   * Replace all references to the old constant pool with references to the new
   * constant pool
   */
  public void replaceConstantPool(ConstantPoolGen old_cp, ConstantPoolGen new_cp) {
    for (InstructionHandle ih = start; ih != null; ih = ih.next) {
      Instruction i = ih.instruction;

      if (i instanceof CPInstruction) {
        CPInstruction ci = (CPInstruction) i;
        Constant c = old_cp.getConstant(ci.getIndex());
        ci.setIndex(new_cp.addConstant(c, old_cp));
      }
    }
  }

  private void clear() {
    start = end = null;
    length = 0;
  }

  /**
   * Delete contents of list. Provides besser memory utilization,
   * because the system then may reuse the instruction handles. This
   * method is typically called right after
   * <href="MethodGen.html#getMethod()">MethodGen.getMethod()</a>.
   */
  public void dispose() {
    // Traverse in reverse order, because ih.next is overwritten
    for (InstructionHandle ih = end; ih != null; ih = ih.prev)
      /* Causes BranchInstructions to release target and targeters, because it
       * calls dispose() on the contained instruction.
       */ {
      ih.dispose();
    }

    clear();
  }

  /**
   * @return start of list
   */
  public InstructionHandle getStart() {
    return start;
  }

  /**
   * @return end of list
   */
  public InstructionHandle getEnd() {
    return end;
  }

  /**
   * @return length of list (Number of instructions, not bytes)
   */
  public int getLength() {
    return length;
  }

  /**
   * @return length of list (Number of instructions, not bytes)
   */
  public int size() {
    return length;
  }

  /**
   * Redirect all references from old_target to new_target, i.e., update targets
   * of branch instructions.
   *
   * @param old_target the old target instruction handle
   * @param new_target the new target instruction handle
   */
  public void redirectBranches(InstructionHandle old_target,
      InstructionHandle new_target) {
    for (InstructionHandle ih = start; ih != null; ih = ih.next) {
      Instruction i = ih.getInstruction();

      if (i instanceof BranchInstruction) {
        BranchInstruction b = (BranchInstruction) i;
        InstructionHandle target = b.getTarget();

        if (target == old_target) {
          b.setTarget(new_target);
        }

        if (b instanceof Select) { // Either LOOKUPSWITCH or TABLESWITCH
          InstructionHandle[] targets = ((Select) b).getTargets();

          for (int j = 0; j < targets.length; j++) // Update targets
          {
            if (targets[j] == old_target) {
              ((Select) b).setTarget(j, new_target);
            }
          }
        }
      }
    }
  }

  /**
   * Redirect all references of local variables from old_target to new_target.
   *
   * @param lg array of local variables
   * @param old_target the old target instruction handle
   * @param new_target the new target instruction handle
   * @see MethodGen
   */
  public void redirectLocalVariables(LocalVariableGen[] lg,
      InstructionHandle old_target,
      InstructionHandle new_target) {
    for (int i = 0; i < lg.length; i++) {
      InstructionHandle start = lg[i].getStart();
      InstructionHandle end = lg[i].getEnd();

      if (start == old_target) {
        lg[i].setStart(new_target);
      }

      if (end == old_target) {
        lg[i].setEnd(new_target);
      }
    }
  }

  /**
   * Redirect all references of exception handlers from old_target to new_target.
   *
   * @param exceptions array of exception handlers
   * @param old_target the old target instruction handle
   * @param new_target the new target instruction handle
   * @see MethodGen
   */
  public void redirectExceptionHandlers(CodeExceptionGen[] exceptions,
      InstructionHandle old_target,
      InstructionHandle new_target) {
    for (int i = 0; i < exceptions.length; i++) {
      if (exceptions[i].getStartPC() == old_target) {
        exceptions[i].setStartPC(new_target);
      }

      if (exceptions[i].getEndPC() == old_target) {
        exceptions[i].setEndPC(new_target);
      }

      if (exceptions[i].getHandlerPC() == old_target) {
        exceptions[i].setHandlerPC(new_target);
      }
    }
  }

  private ArrayList observers;

  /**
   * Add observer for this object.
   */
  public void addObserver(InstructionListObserver o) {
    if (observers == null) {
      observers = new ArrayList();
    }

    observers.add(o);
  }

  /**
   * Remove observer for this object.
   */
  public void removeObserver(InstructionListObserver o) {
    if (observers != null) {
      observers.remove(o);
    }
  }

  /**
   * Call notify() method on all observers. This method is not called
   * automatically whenever the state has changed, but has to be
   * called by the user after he has finished editing the object.
   */
  public void update() {
    if (observers != null) {
      for (Iterator e = observers.iterator(); e.hasNext(); ) {
        ((InstructionListObserver) e.next()).notify(this);
      }
    }
  }
}
